Water-Soluble Luminescent Hybrid Composites Consisting of Oligosilsesquioxanes and Lanthanide Complexes and their Sensing Ability for Cu2+

Water-soluble hybrid composites with great potential for selective and sensitive sensing and that are obtained through simple, rapid, and environmentally friendly methods are highly desirable and remain a challenging task. Herein, we present luminescent hybrid composites that were realized by linking Na-3[Ln(dpa)(3)] (dpa=2,6-pyridinedicarboxylic acid) to octa-amino functionalized polyhedral oligomeric silsesquioxane (POSS-NH2) through hydrogen-bonding interactions between the oxygen atoms of the carboxylate groups of dpa and the hydrogen-bond-donor amino groups. The resulting hybrid composites Ln(dpa)(3)@POSS-NH2 are highly soluble in aqueous solutions and the quantum yield of Eu(dpa)(3)@POSS-NH2 is as high as 56.5% or 46.3% in the solid state and in aqueous solution, respectively, as determined by using the integrating sphere method. The novel water-soluble luminescent hybrid composites exhibit high thermal and photostability, and the emitted colors of the resulting hybrid composite can be finely tuned by changing the Eu3+/Tb3+ ratio. Interestingly, Eu(dpa)(3)@POSS-NH2 hybrid composites exhibited an effective switch-off fluorescence response to Cu2+ over other common metal ions in aqueous media.